1. Field of the Invention
The present invention relates to an inertia sensor for detecting an angular velocity and acceleration, and a detector device thereof.
2. Description of the Related Art
An inertia sensor has been known that is attached to an object and can detect acceleration and an angular velocity which are produced when the object carries out acceleration movement and angular velocity movement.
This inertia sensor detects individual acceleration per each axial direction at X-axis, Y-axis, or Z-axis defined as the 3-dimensional space, and detects individually the angular velocity per each axis which serves as rotation axis, whereby the acceleration and the angular velocities of the object moving in the 3-dimensional space has been detected.
In recent years, as an inertia sensor which can detect acceleration and an angular velocity of an object simultaneously, a sensor is proposed using a structural body having a movable body (oscillator) which is displaced in accordance with acceleration movement and angular velocity movement of an object.
As for this inertia sensor, in the case where the X-axis, the Y-axis, and the Z-axis which intersect orthogonally to one another are defined in the 3-dimensional space, in a situation where the movable body is vibrated at predetermined time cycle in the Z-axis direction, and when the object carries out angular velocity movement by assuming the X-axis or the Y-axis as a rotation axis, then Coriolis force acting in a direction orthogonal to a movement direction of the object is detected to find the angular velocity assuming the Y-axis or the X-axis as a central axis and the angular velocity in the X-axis direction, or the Y-axis direction (see Japanese Patent No. 3549590, Patent Document 1, and Japanese Patent No. 3585959, Patent Document 2, for example).
As for this type of inertia sensor, for example, in a situation where the vibrator of this inertia sensor is vibrated at predetermined time cycle in the Z-axis direction and in the case where the object having attached thereto this acceleration and angular velocity sensor carries out the angular velocity movement by assuming the X-axis as a rotation axis, a physical phenomenon in which the Coriolis force towards the Y-axis direction acts on the movable body, is used, and the displacement amounts of the movable body in accordance with a magnitude of this Coriolis force is detected, whereby a magnitude of the angular velocity which acts on the object by assuming the X-axis as a rotation axis may be detected.
However, since these inertia sensors separate the displacement of the acceleration and the angular velocity obtained from one movable body by means of signal processing, it is not possible to obtain a sufficient S/N ratio (Signal to Noise Ratio) with respect to a cross-axis sensitivity and a disturbance noise, and an usable application is limited.
Then, the applicant of the present invention has proposed a small inertia sensor which can obtain the sufficient S/N ratio with respect to the cross-axis sensitivity or the disturbance noise, and can detect 3-axis acceleration and a 3-axis angular velocity (see Japanese Patent Application Publication No. JP 2006-167760, Patent Document 3).
Since the inertia sensor as disclosed in Patent Document 3 has a plurality of movable bodies (vibrators), it is necessary to use a detector circuit for detecting the displacement of the plurality of movable bodies.
As a technology of detecting a capacitance value of a variable capacitance element constituted by a plurality of movable bodies by means of few detection systems, there is a technology of detecting a difference in capacitance value between two variable capacitance elements constituted by the respective movable bodies and detecting the displacement of each movable body as disclosed in Japanese Patent Application Publication No. JP H10-239196, Patent Document 4.
However, the structural body in Patent Document 4 is a structural body used in order to detect only the acceleration, does not need to vibrate each movable body, and is different in structure from the structural body of Patent Document 3 which is used in order to detect not only the acceleration but also the angular velocity. Thus, it is difficult to apply the technology of Patent Document 4 to the structural body as disclosed in Patent Document 3.